1. Field of the Invention
The present invention relates to a method and to an apparatus for recognizing digital information in a digital information transmission, particularly an information transmission in mobile radio communications systems.
2. Description of the Prior Art
Speech information, data information and image information are the forms of information which are to be transmitted in known, wire-bound communications systems and in a future mobile ratio communications systems. Given a transmission of information, particularly digitized information, in a mobile radio communications system, a problem arises in that, due to so-called multi-path propagation on the radio path, fading arises which can cause information bit errors during transmission.
Techniques are known by which a sampling pulse is derived at the respective receiver from the received digital information and is employed for placing a sampling time into the respective area of an information element in which the pulse to be sampled, and which represents the information element, assumes its suspected, quasi-stationary state, cf., for example, see the German allowed and published application Ser. No. 1,804,719. These known methods, however, have the disadvantage that, in those cases in which pulses representing information elements are distorted in amplitude and/or in phase due to disruptive influence, a bit error can be simulated precisely in the respective area sampled, although the appertaining pulse, when viewed as a whole, can be free of error.
In mobile communications systems previously designed, attempts are made to provide as favorable as possible a bit error rate by applying different encoding methods, for example, "forward error correcting". This philosophy, however, is opposed by the attempts to achieve a standardization of the operating modes.